A typical disc drive stores and retrieves data from a storage disc using read/write devices. The disc drive also includes an actuator which includes at least one actuator arm and a voice coil motor for controllably moving the read/write devices. The voice coil motor includes a moving coil and a fixed magnet. In a rotary actuator, one end of an actuator arm is mounted to at least one suspension and the other end of the actuator arm is pivoted and carries the coil. Each suspension supports a read/write device. The amount of current applied to the coil determines the movement of the actuator arm and consequently the position of the read/write device with respect to each disc surface.
There are various methods of attaching the suspension to an actuator arm. Some of the methods include the use of adhesives, screws, clamps, and swaging. Currently, the predominant method for attaching suspensions to actuator arms is a process referred to as swaging. This is described by Hinlein in the U.S. Pat. No. 5,153,794 issued Oct. 6, 1992. In one known swaging method two suspensions are attached to an actuator arm by means of two bosses having short tubular stems each of which are aligned through holes in the suspensions and into a through hole on opposing sides of the actuator arm. The stems of the bosses are thereafter forcibly expanded by driving a ball bearing through the tubular stems. This creates a mechanical bond which is reinforced by welding the baseplate of the boss to the suspension.
It is known that there are several limitations associated with the swaging method, for example, a certain thickness of the actuator arm is required to allow for the expansion of the boss into the actuator arm and thereby form the mechanical joint. The force exerted on the actuator arm by the swaging process may crack the actuator arm, resulting in lowered production yield. The boss is also relatively expensive as it forms about ten percent of the assembly cost.
Adhesives may be used to join actuator arms to suspensions, but are not popular as it creates outgassing problems amongst others. Welding is also not commonly used particularly because the actuator arms and suspensions are usually made of metallurgically incompatible materials, the welding of which is well known to be fraught with difficulties.